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N. PETERS. PHOTOJJTHOGRAPHER, WASHINGTON D C @luitentstre stent @fitta IMPROVEMENT IN BRIDGES.

SPECIFICATION. TO .ALL WHOM I'l MAY CONCERN.:

Be it known that I, 0. Gr. LEOPOLD, of the city of Cincinnati, Hamilton county, State-ofOhio, havieiinvented a new and useful Improvement in Bridges ;A and I do hereby declare that the following is a full and exact,` description thereof, which lwill enable'others skilled in the art to make and use theisame, reference being had to the accompanying drawings, forming part of this specification, in which- VFigure lis a perspective view of my improved bridge. Figure2 is a vertical longitudinal section of 4the same. Figure 3 is a vertical cross-section of the same. Figure 4 is a top cr. plan view of the same. Figure 5 is a detail view of a portion of a girder illustrating one mode of joiningthe plates of the central rib.

Figures 6, 7, and 8, are cross-sections of the side girders illustrating different modes v.of forming the top rail of the girders. i Figures 9, 10, 11, 12, are ldetail views illustrating diiferent modes of joining tlie plates. Figures 13, 14, 15, are detail views illustrating the old manner ofjoining the plates. c Figure 16 is a detail view illustrating one mode of forming the cr0ss-ties. Figure 17 is a cross-section of lig. 16. Similar letters of reference indicate like parts. The construction of` this bridge is based upon the theory of theineutral line or point ofgravity of the crosssection of a loaded beam supported at its ends, and for its form the doublefshaped Icross-section was adopted as the strongest with reference to the metal expended. To these as the leading ideas thewholestructure was made to conform in its combination as well as in all its minor parts, and was made to serve the purpose aimed` at, viz, the production of a strong, durable, and comparatively light structure. Y

The beams of the bridge consist of a combination of plate and angle item-which by means of rivetsare" formed into a parallel wrought-iron girder, A, whose cross-section resemblesthe double Tthus: I. Thelower stringer or ange, a", is flat iron of proportional strength to the span of the bridge, `towhich by means of angle iron, a2, the central rib or vertical plate, a3, of the T is fastened. The thickness and heightof the rib, ai, is`

also made proportional to the respective span. The top rail or flange, a, of ithe beam may: be made either of flat iron, as seen in iig. 1, or of plate in tubular form as illustrated in figs. 5,6, 7, 8, the latter preferred `for` reason of compensating (with less expenditure ofmetal) for the diierence in the strength that wrought iron prei 'sente to au expansive strain, thus balancing the4 resistance of that portion of the cross-sectionof the girder lying above the point of gravity to that lying below the same, or, in other words, bringing the neutral line in i them'iddle of the cross-section of the beam. This line, from the manner in which theiload operates upon the i resisting strength of the beam, being the line of stability, is selected for the attachment of the roadway, thus laying the loadin the strongest point of the girder. The height of the girders', A, being` determined by and proportional to the span of the bridge, and inconformity to the best'rules of the-most approved` engineering` authorities, it also determines the relative position 'of' the lateral T-shaped braces, B';their distance from` each other being-proportional to the height of the girder's, A, subdivides thexlatter into square fields orsections, thus imparting the requisite stiffness to the central rib, a3, of the girder. f These braces, B,presenting at the end view of the bridge, with the girders as heads, also a double Tl'form, have likewise'a double` ;T'shaped`vcross i section produced by a combination of plate and angle iron. The braces are fastened `to thegirders by` means of rivets; thus that while riveted fully-at each end (irrespective head of tbel'l, to'theplates ofthe central rib` of the girder above the point of gravity or the `.neutral line, they are only fastened near fthell lower ange by, means of a few rivets, thereby avoiding an `unnecessary and rather injurious weakening of thegirder atthose i points where the expansive force is operating on its strength, and still 'accomplish the object of `keeping `the lower parts of thebraces in their proper relative` positions. These braces are, in their turn, stii'ened `iii the i i centre of Itheir length, or half-way between the two principal girders, by a longitudinalbar, C, of l a double Tf shaped cross-section, and of a height to correspond with the bars or carriers, I), which are fastened al: the point p of gravity or line of stability of the central rib of the main `girders, thus affording an additional or` centralsupf porting point for` the lateral ties or sills, E, of the roadway." On the inner side of each girder, LA, at the line stability, a flat liar, D, is fastened by means of angle iron and rivets to the central ribg'as, of` the :lf-shaped main girders, A, which serves as carrier to the cross-ties or sills, E, of the roadway, thus loading the girders ot' the bridge at the neutral line where the two opposite forces-compression and expansion-meet, that operate upon a loaded beam according to the established principle by the experiments of Hodgekisons, Barlow, Fairbairn, Stephenson, Weisbach, and other standard authorities, this line being the line of stability, from the fact that in case of breakage this point of the cross-section of the girder will suiier comparatively the least injury. These i plates or'bars, D, are braced at equal distances b'y small triangular brackets, F, formed of plate and angle iron,

in each and all of the intervening spaces between each pair of contiguous lateral braces, as indicated by dotted lines in iig. 2. Each section or field of the lateral bracing of the bridge receives additional strength from the l diagonal tie-rods, G, fastening the two opposite points or corners of each pair of contiguous braces, B, on each side ofthe central longitudinal brace bar, YC, together. In execution of the whole combination a due regard is i had for such forms, sizes, and manner of workmanship, as the teachings of experience have pointed out; thus no joints in the lower stringers or plates, or in fact in any-portionof the bridge exposed tothe expansive strain, are formed on a straight or right angular line, but either on a diagonal or circular line, as seen at a5, iig. 1, and` illustrated -in figs. 9 to 12 inclusive, thereby obviating the weakening of those points in coniparison to the full strength of the solid metal in the proportiori as 1 to 8. At points situated above the neutral line, or in parts where the compressive force is operating, joints in straight lines, as customary, may be made, as not interfering materiallywith the-strength of ther bridge. -The upper rail, a4, head of the'l or tcp of the principal girders are to bemade tubular, in preference to solid flat bar or plate, as this form affords greater strength with comparatively less expenditure of metal under a compressive strain. The particular form of this tube is not an essential feature, but may be either circular, elliptical, triangular, square, oblong, or of any other similar form by which the same effect is obtained.` For the protection or in order toreduce the thickness of the lower Stringer, al, and increase proportionally its width with reference to its requisite strength, platesforming, with the stringer for a base, a triangle in the cross-section may be introduced, thus affording additional lateral stiffness, and at the same time throwing ed' the water. The beams orthe cross-ties (sills) E, of the roadway, I would either make of metal placed on wooden blocks, so as to preserve a certain requisite elasticityY to the rails of a railroad, or form them of three parts of heavy planking with a light metal plate for covexgas' illustrated in figs. 16 and 17, thus' producing lighter hollow rails and decreasing thereby the dead load on the bridge, giving protection to the wood by admitting a current of air through it, sheltering the wood against the iniue'nces of" the Wet resting on the beam, and atthe same time preventing the timber 4from being cut or otherwise tampered with from malicious intents. These sills or beams, E,shonld be of height sutiicient to prevent the track-rail, H, or platform for roadway, from resting on the lateral braces, B, but should be exclusively, and in accordance with the principle involved, supported by the bars D andC at a level and in line with the neutral or line of stability of the principal girders, A. The girders, A, of the bridge are not bolted or anchored to the abutments, I, but are held and made to slide freely on rollers, J, in shoes or Hang-ed sockets, which overlap the lower flanges, a1, of the girders, A.

Making the attached drawings a part'of my description, as illustrating more fully and comprehensibly the parts and combination of my parallel wrought-iron girder bridge, Il lay no claim to the principles applied, or any of its known orotherwise hereinbefore employed forms of material, but claim as my invention, asbest suited to the specic purposes in view, viz, strengthand lightness of structure.

I claim as new, and desire to secure by Letters Patent-'- 1. The general arrangement and combination of wrought angle iron and plate ina bridge, sovas to present in the cross-section of the girders and all other essential parts of the bridge, the double-T form, substantially as described. i

-2. The arrangement and adaptation of the b ar D to the central rib a3, in such a manner that the platform or roadway of the bridge 'shall be located at or near the line of stability, or neutral line of the girder, substantially as described.

3. And in combination with the above, I claim the lateralbracing for the support of the roadway, substantially as described. v

4. Making, in the combination of the double 'l of the bridge girder, the upper Stringer or head of the same ofeither a flat bar or a hollow tube of any form, substantially as described. I 5. Making the sills or cross-ties of the roadway of hollow wooden beams instead of solid timber, and covering the same with metal plate, substantiallyas described.

The above specification of my invention signed by me this fourteenth day of November, 1865.

O. G. LEOPOLD.

Witnesses:

JAMES Fosrnn, Jr., Orro HEINEMANN. 

